My various projects that may be of interest to others.
Dedicated to my brother Stan, Apr 16, 1955- Dec 4, 2010

Sunday, February 14, 2010

Rion Greenhouse

The Rion greenhouse is a fun to assemble kit. The whole thing is made from extruded PVC shapes and double wall polycarbonate panels. It is available as small as 8 x 8 feet, and can be lengthened in 4 foot increments. We chose to make a 16 foot long version. A nice feature is the automatic vents that use an actuator that requires no power. A fluid inside a cylinder expands to drive a piston which opens the window. What is not provided is a foundation. That is left up to the builder. Most use a frame of landscape timbers, which is OK. However, I wanted a more durable foundation, and I wanted more headroom inside. One drawback of this greenhouse is a door which is only 5 foot 4 inches, and just barely 6 feet inside. I'm 5 foot 10 inches and did not want to duck to get through the door.
Another problem is that my building site was not level. I solved these issues by building a concrete block wall to raise the greenhouse up 12 inches. This required me to make the doors taller. I accomplished this by ordering extra parts from which I made the additional lower sections in the doors.
The threshold had to be modified too, as it originally went straight across the bottom. I cut the threshold parts and ran them down the sides of the wall instead. Then I poured a concrete threshold, which also supports the hinges.
Then I had another idea. Why not fill the hollow wall extrusions with concrete? Then also add a little rebar inside as well. I left about a foot of rebar sticking out, which I then cemented inside the hollow spaces in the block. This added a couple hundred pounds to the lightweight greenhouse structure and really stiffened things up. We live in a high wind area and I did not want my greenhouse to blow away! 2 years and many storms later, it has proven to be surprisingly solid. The concrete/rebar idea was also useful for attaching the modified threshold parts to each other, and to the foundation.
The unheated greenhouse also performs surprisingly well! This is a picture of lettuce and spinach thriving inside, in early November.

We are still learning how to best run a greenhouse, studying books like "Four Season Harvest" by Eliot Coleman. He does remarkable things with an unheated greenhouse in Maine, so we should be at least able to duplicate his results in milder Pennsylvania.

I can see why hers failed catastrophically, and my greenhouse has not. The reasons:

Colder temperatures. For me, temperatures at or below 0F (-17.8C) are rare. The plastic Rion uses becomes brittle at those temperatures.

The sunroom has more stress on its parts. The greenhouse is 8'6" wide, and the sunroom is 6'5" wide. However, the sunroom is designed like half a greenhouse. If it were a greenhouse, it would be a nearly 13' wide greenhouse, or 150% wider than the greenhouse. But the stress on the roof members is not 150% more, it is about 450% more! To calculate this, I used the flexural strength formula: Stress= (3 x Load x Length) / (Beam width x Beam thickness) Yet the pieces used in the sunroom are exactly the same as in the greenhouse.

The sunroom also lacks a key strength member that the greenhouse has: This cable spanning the top section of the greenhouse roof. This puts most of the greenhouse roof under compression, which is why the greenhouse can support considerable snow loads.

It appears that Rion made a classic engineering error, one of scaling. They took a sound design, that if the greenhouse, and scaled it larger without considering the higher stresses on the scaled up sunroom.

Finally, here are the unsightly openings at the bottom of the roof panels that Karen complained about. She is correct. This is unacceptable in a living space. I filled my gaps with Great Stuff, which lasted a few years. I have to do it again.

8 comments:

Im so glad i found your page! I also live in PA. (South Central) and have been looking at the Rion greenhouses for a long time. I have a pretty big garden, but so many bugs its crazy.. i try to grow organic. and have tryed lots of things to get rid or at least keep the bugs out. SO i must ask, do you get many bugs in your greenhouse?

Just a quick suggestion; in addition to screening the vents we use 2 potted mums one at each large air vent an introduce green lacewings or ladybugs (specifically Coleomegilla maculata) every other Spring. Result in Central Michigan . . . .no bugs.

I only use the greenhouse in the early spring and fall, but it should keep most bugs out if you screen the vents. The door seals tightly. I do not use it much in the summer for it gets intolerably hot for most plants. However, you can buy sunshades that cover the entire greenhouse. If you buy a Rion, I recommend getting the white model, for they hold up better under strong sunshine. While mine has held up OK, I would get the white one if I was to do it all over.I have grown tomatoes inside mine, but they pretty much took over the whole greenhouse. Once the plants start growing, the greenhouse gets crowded in a hurry!

Hi Robert.. I'm wondering how your greenhouse did after this harsh winter. We had a Rion Sunroom, very much like your greenhouse only it attached to our home and was 3 1/2 years old.. the top of it totally collapsed during the night about 6 weeks ago.. It was sitting on a very stable, level deck we built just for the sunroom. We were plagued with problems from the start.. leaks, door wouldn't seal, panels that popped through, parts that popped loose. Since they're warranted for 7 years, we contacted Rion about the collapse but have gotten nothing but the runaround.. it was the frame that broke. It looked like it broke on both ends and the rest just imploded. I hope your's fared better than ours did!

Hi Robert.. I find your analysis very interesting! What you suggest makes a lot of sense.. It's now been about 6 months since our's collapsed, and I have gotten no where with the Rion company. They have sent my claim on to the Palmar Industries in Israel, who of course, have just ignored it. So unfortunate to buy something from an American company only to have them pass your problems off to a company in Israel.. Your foundation looks awesome! I hope your greenhouse is still working for you.. Lettuce growing in November is awesome!!!